Combined fuel and ignition means for spark-ignition internal combustion engines are known. Typical examples of arrangements involving combined fuel injection and ignition means are disclosed in U.S. Pat. No. 4,967,708 (Linder et al), EP 0 632 198 (Suzuki), U.S. Pat. No. 5,497,744 (Nagaosa et al), and U.S. Pat. No. 5,730,100 (Bergsten).
In each of these arrangements, the fuel and high voltage ignition follow a common path through the device. Typically, fuel is delivered through a fuel delivery port defined between a valve seat and a valve needle. The valve needle is of electrically conductive material so as to provide the ignition path. This arrangement thus provides the common path for the fuel and the high voltage energy.
In such devices the valve stem is believed to provide relatively high levels of capacitance within the ignition circuit. This can lead to high level of electrical noise radiating from such devices. In some arrangements there can also be secondary sparking that occurs between the moving components of the valve needle during ignition.